The present invention relates to a projection copying apparatus for reproducing microfilmed originals on a light-tightly coverable projection screen, and also for producing
More particularly, it relates to such a projection copying apparatus which is used for the above specified purposes and in which the original is copied completely or partially by means of an arrangement suitable for copying of dotted originals.
The German document DE-OS 3,309,578 described a projection copying apparatus in which the penetration of exterior light through the projection screen during the copying process is prevented by means of a shade which covers the projection screen in a light-tight manner. Indication and selection of portions to be copied from the enlargement of the microfilmed originals are performed in this apparatus by electromechanical elements, for example by two potentiometers with axes each coupled with a pointer.
The utilization of mechanical or electromechanical structural elements has the disadvantage that the frequency of maintenance which depends on the wear of the structural parts is relatively high. In addition, due to the mechanical inertia of the shade during its pulling, the time of the copying cycle is increased.